import defined from '../../Core/defined.js'
import DeveloperError from '../../Core/DeveloperError.js'
import knockout from '../../ThirdParty/knockout.js'
import createCommand from '../createCommand.js'

/**
 * The view model for {@link HomeButton}.
 * @alias HomeButtonViewModel
 * @constructor
 *
 * @param {Scene} scene The scene instance to use.
 * @param {Number} [duration] The duration of the camera flight in seconds.
 */
function HomeButtonViewModel(scene, duration) {
  // >>includeStart('debug', pragmas.debug);
  if (!defined(scene)) {
    throw new DeveloperError('scene is required.')
  }
  // >>includeEnd('debug');

  this._scene = scene
  this._duration = duration

  const that = this
  this._command = createCommand(function() {
    that._scene.camera.flyHome(that._duration)
  })

  /**
   * Gets or sets the tooltip.  This property is observable.
   *
   * @type {String}
   */
  this.tooltip = 'View Home'

  knockout.track(this, ['tooltip'])
}

Object.defineProperties(HomeButtonViewModel.prototype, {
  /**
   * Gets the scene to control.
   * @memberof HomeButtonViewModel.prototype
   *
   * @type {Scene}
   */
  scene: {
    get: function() {
      return this._scene
    }
  },

  /**
   * Gets the Command that is executed when the button is clicked.
   * @memberof HomeButtonViewModel.prototype
   *
   * @type {Command}
   */
  command: {
    get: function() {
      return this._command
    }
  },

  /**
   * Gets or sets the the duration of the camera flight in seconds.
   * A value of zero causes the camera to instantly switch to home view.
   * The duration will be computed based on the distance when undefined.
   * @memberof HomeButtonViewModel.prototype
   *
   * @type {Number|undefined}
   */
  duration: {
    get: function() {
      return this._duration
    },
    set: function(value) {
      // >>includeStart('debug', pragmas.debug);
      if (defined(value) && value < 0) {
        throw new DeveloperError('value must be positive.')
      }
      // >>includeEnd('debug');

      this._duration = value
    }
  }
})
export default HomeButtonViewModel
